1. Field of the Invention
This invention relates to electrophotographic reproduction apparatus and methods for registering sheets and more particularly to apparatus and methods for control of a stepper motor drive for controlling movement of a receiver sheet into transfer relationship with an image-bearing member that supports an image to be transferred to the receiver sheet.
2. Brief Description of Available Systems
In known electrophotographic copier, printers or duplicators the problem of accurate registration of a receiver sheet with a moving member supporting an image for transfer to the sheet is well known. In this regard, reference is made to U.S. Pat. No. 5,322,273, the contents of which are incorporated herein by reference.
Typically, an electrophotographic latent image is formed on the member and this image is toned and then transferred to a receiver sheet directly or transferred to an intermediate image-bearing member and then to the receiver sheet. In moving of the receiver sheet into transfer relationship with the image-bearing member, it is important to adjust the sheet for skew. Once the skew of the sheet is corrected, it is advanced by rollers driven by stepper motors towards the image-bearing member. During the skew control adjustment, the adjustment is implemented by selectively driving the stepper motor driven rollers, which are controlled independently of movement of the image-bearing member. Typically, movement of the receiver sheet and operations performed thereon by various stations are controlled using one or more encoders. Known registration control systems use a transfer roller with which an encoder wheel is associated. This encoder is used for controlling registration of the sheet. For instance, a registration apparatus is disclosed in U.S. Pat. No. 5,731,680, the contents of which are incorporated herein by reference.
However, previous registration apparatus and methods have been limited in that they can only process and register receiver sheets that are no longer than a predetermined maximum length. Typically, the hardware of known systems has been optimized to accommodate the most popular sheet sizes, such as those having lengths of 8.5 inches or 17 inches. These registration systems have been unable to accommodate and register receiver sheets that are longer than this predetermined optimal receiver length. For example, systems optimized for 17-inch sheets have been unable to accommodate 18-inch sheets. Although there is an increasing need for accommodation of 18-inch receiver sheets in electrophotographic reproduction apparatus, the vast majority of demand is still for accommodation of receiver sheets having lengths of 17 inches or less. It is, therefore, an object of the invention to provide improved methods and apparatus for ensuring accurate registration of receiver sheets that are somewhat longer than the predetermined optimal receiver length for which specific registration assembly hardware is designed.
In accordance with one aspect of the invention, there is provided an apparatus for moving a receiver having a lead edge and a trailing edge from an upstream engaging nip into registered relationship with an image-bearing member moving at an image-bearing member speed. The apparatus includes a motor, a drive member operable to engage the receiver, and a drive coupling connecting the motor with the drive member. A controller is provided to drive the motor in accordance with a first velocity profile if the receiver is of a predetermined optimal receiver length, and to drive the motor in accordance with a second velocity profile if the receiver is longer than the predetermined optimal receiver length.
In accordance with another aspect of the invention, there is provided an apparatus for moving a receiver having a lead edge, a trailing edge, and a length of more than the predetermined optimal receiver length, from an upstream engaging nip into registered relationship with an image-bearing member moving at an image-bearing member speed. The apparatus includes a motor, a drive member operable to engage the receiver, and a drive coupling connecting the motor with the drive member. A sensor is included to detect the lead edge of the receiver. A controller drives a motor to (1) move the drive member into engagement with the receiver when the lead edge of the receiver has moved a distance beyond the sensor, the distance being sufficiently large that the trailing edge of the receiver is released from the nip before the receiver is brought to a stop; (2) stop the receiver; and (3) deliver the receiver to the image-bearing member at the proper time and at a speed substantially equal to the image-bearing member speed.
In accordance with yet another aspect of the invention, there is provided a method of moving a receiver having a lead edge and a trailing edge from an upstream engaging nip into registered relationship with a moving image-bearing member moving at an image-bearing member speed. First, a motor, a drive member operable to engage the motor, and a drive coupling connecting the motor with the drive member are provided. The a controller is provided to drive the motor. The controller is operated in accordance with a first velocity profile if the receiver is of the predetermined optimal receiver length, and the controller is operated in accordance with a second velocity profile if the receiver is longer than the predetermined optimal receiver length.
In accordance with a further aspect of the invention, there is provided a method of moving a receiver having a lead edge, a trailing edge, and a length of more than the predetermined optimal receiver length, from an upstream engaging nip into registered relationship with a moving image-bearing member moving at an image-bearing member speed. First, the lead edge of the receiver is detected. A drive member is then moved into engagement with the receiver when the lead edge has moved a distance beyond the sensor, the distance being sufficiently large that the trailing edge of the receiver is released from the nip before the receiver is brought to a stop. Next, the receiver is stopped. The receiver is then delivered to the image-bearing member at the proper time and at a speed substantially equal to the image-bearing member speed.
The invention and its various advantages will become more apparent to those skilled in the art from the ensuing detailed description of preferred embodiments, reference being made to the accompanying drawings.